Diagnostic Accuracy of Neutrophil Gelatinase-Associated Lipocalin in Peritoneal Effluent and Ascitic Fluid for Early Detection of Peritonitis: A Systematic Review and Meta-Analysis

Background/Objectives: Peritonitis remains a leading cause of morbidity and mortality in patients undergoing peritoneal dialysis and those with cirrhotic ascites. Neutrophil gelatinase-associated lipocalin (NGAL) is a promising early biomarker. We conducted a systematic review and meta-analysis to determine NGAL's diagnostic performance for peritoneal dialysis-associated peritonitis (PDAP) and spontaneous bacterial peritonitis (SBP). Methods: Following PRISMA-DTA guidelines and PROSPERO registration (CRD420251105563), six databases were searched to 30 June 2025. Studies with extractable 2×2 data reporting peritoneal or ascitic fluid NGAL measurements against standard reference criteria were included. Pooled sensitivity, specificity, diagnostic odds ratio (DOR), and HSROC AUC were estimated using bivariate random-effects models. Heterogeneity was explored through prespecified subgroup analyses. Results: Thirteen studies (2013–2024) met inclusion; ten (573 cases, 833 controls) entered metaanalysis. Pooled sensitivity was 0.948 (95% CI 0.901–0.973) and specificity 0.864 (0.704–0.944); HSROC AUC was 0.95 and DOR 90.59. Likelihood ratios were LR⁺ 6.96 and LR⁻ 0.06. Accuracy was similar for PDAP vs SBP (Se 0.964 vs 0.932; Sp 0.882 vs 0.849; subgroup pvalues >0.3), with heterogeneity concentrated in specificity. By platform, ELISA showed balanced performance (Se 0.947; Sp 0.910), pointofcare (POC) tests the highest sensitivity (0.977) with wider specificity uncertainty, and automated immunoassays lower specificity (0.691); a global LRT supported platform differences (p=0.0098). Conclusions: Peritoneal/ascitic NGAL provides rapid, accurate discrimination of peritonitis across SBP and PDAP, with particularly strong rule‑out capability. Implementation should prioritize assay‑specific (two‑threshold) decision points, standardized dwell time and pre‑analytics, and prospective multicenter impact studies to embed NGAL within guideline‑concordant diagnostic pathways.